The idea was to see how environment influenced development. Could a chimp grow up to behave like a human? Or even think it was a human? On June 26, 1931, comparative psychologist Winthrop Niles Kellogg and his wife welcomed a new arrival home: not a human infant, but a baby chimpanzee. The couple planned to raise the chimp, Gua, together with their own baby boy, Donald.Kellogg always had dreamed of performing such an observation since his student days. He was engrossed by wild children, or those brought up with no human contact, oftentimes in nature.Abandoning a human child in the wilderness would be ethically inexcusable, Kellogg knew, so he opted to experiment on the contrary framework i.e. bringing an infant animal into civilization.For the next nine months, for 12 hours a day and seven days a week, Kellogg and his wife observed determined tests on Donald and Gua.As such, The Psychological Record authors write, the Kellogg’s' experiment "probably succeeded better than any study before its time in demonstrating the limitations heredity placed on an organism regardless of environmental opportunities as well as the developmental gains that could be made in enriched environments."

But eventually, Gua hit a cognitive wall: no amount of training or nurturing could overcome the fact that, genetically, she was a chimpanzee. "Our final concern is why the project ended like this.We are told only that the study was terminated on March 28, 1932, when Gua was returned to the Orange Park primate colony through a gradual rehabilitating process. But as for why, the Kelloggs, who are so specific on so many other points, leave the reader wondering".The experiment was meant to last for 5 years, following the growth of each child, but after just 9 months, Kellogg decided to ended it abruptly and mysteriously.It could be that the Kellogg was really drained from nine months of non-stop parenting and scientific work. Or perhaps it was the fact that Gua was becoming stronger and less manageable, and that Mrs. and Dr. Kellogg feared that she might be harmful for her human brother. However, one other probability comes to mind, the authors point out: while Gua showed no signs of learning human languages, her brother Donald had begun imitating chimp’s voices. "In short, the language retardation in Donald may have brought an end to the study”.

Gua was placed back in the care of a primate center in Florida, but sadly passed away less than a year after leaving her adoptive family after a bad case of pneumonia. However, her impact on the study of environment and hereditary development remains an essential stepping-stone in the progress of biological and psychological theory.Kellogg and his wife wrote a book, "The Ape and The Child", which chronicles their distinctive and unprecedented experiment.